Harrison Ford holds a young ape during his segment of Showtime's 'Years of Living Dangerously.' (All photos courtesy of Showtime)

Eight years since the Oscar-winning documentary “An Inconvenient Truth” sounded the alarm about global warming, the climate crisis is more critical than ever. The new Showtime series “Years of Living Dangerously” picks up the mantle, enlisting A-list celebrities to serve as correspondents to draw attention to the most pressing climate issues.

“It was really important to make sure we had reach with this series. And we wanted people who were passionate about the issue. But we didn’t want them to give their point of view about it. We wanted them to be asking questions on behalf of the audience,” says executive producer David Gelber.

“We were very selective about the celebrities that we chose. We wanted people who had a real commitment to this. These are not cameo performances,” says executive producer Daniel Abbasi, who added that scientists, while credible, “are not the best communicators in the world. Celebrities are charismatic. They draw people in.”

Harrison Ford, who is on the board of Conservation International, travels to Indonesia to expose illegal deforestation (and both its carbon emission and habitat loss impact). Matt Damon, co-founder of Water.org, explores the devastating consequences of heat waves. Don Cheadle, a United Nations environmental ambassador, investigates severe droughts. Other correspondents include Jessica Alba, America Ferrera, Michael C. Hall. Olivia Munn, and Lesley Stahl of “60 Minutes,” who reports on melting ice in the Arctic.

Arnold Schwarzenegger, also a producer of the series, embeds with a team of elite firefighters as they tackle wildfire outbreaks that have increased in frequency and magnitude. During his time as California’s governor, “I went to the front lines and evacuation centers, talking to firefighters, and became very passionate about it,” he says, explaining why he chose the topic.

“I think the environmental movement only can be successful if we are simple and clear and make it a human story. Scientists would never get the kind of attention that someone in show business gets. When you have the power of communicating that an entertainer or athlete has, you use it for something positive,” says Schwarzenegger, who also emphasized that everyone can do something. "If you build a home, have it solar-powered. The solar today is very inexpensive. Buy a more fuel-efficient car. If you do a re-do of your lights, have LED lights. They can save you 80, 90 percent of your energy bill because they're very energy-efficient. Buy energy-efficient appliances. There are a lot of things that ordinary folks can do to be part of this movement.”

Legislation, of course, is a crucial part of the effort to halt global warming, and Schwarzenegger is quick to point out his accomplishments on that score when he was governor. “We passed a low-carbon fuel standard, a green building initiative to make government buildings more energy-efficient. We passed AB 32, making a commitment to reduce greenhouse gases in California by 25 percent by 2020 and by 85 percent by 2050. We have the Million Solar Roofs program, which will inspire other states and cities to install solar panels,” he says. But he doesn’t take all the credit. “Going back to the '60s in California, governor after governor has always been on board to protect the environment.”

The same might be said of actor Ian Somerhalder. “I’m from the Gulf Coast of Louisiana, the most delicate ecosystem in the country, and I’ve watched it be destroyed. My whole life I’ve been about protecting it,” he says, but he covers a different story in “Years of Living Dangerously” — that of Pastor Rick Joyner, a climate change denier, whose daughter Anna Jane is an environmental activist. “Imagine growing up in a household with a very religious father who is a wildly compassionate man, a very loving man, a very smart man, but his belief system dictates that he doesn't believe in climate change. He ended up cutting off her tuition because he ultimately said that she was being too educated.”

With nearly 16 million Facebook and Twitter followers, Somerhalder is keenly aware of the power of social media and uses it to promote his environmentally oriented Ian Somerhalder Foundation, “leveraging that to create true quantifiable global change,” he says. For him, “This is the single most important story ever told and most important project I’ve been a part of.”

Although he and the other correspondents traveled the globe for their investigative reports, the production endeavored to reduce its carbon footprint by using recycled materials and plant-based food service items like utensils and plates. “It's literally impossible to move around the world without using fossil fuels,” notes Somerhalder. “The message, however, is much, much greater than what we used to create the production.”

Gelber, who first got the idea for it when he and co-executive producer Joel Bach worked at “60 Minutes,” believes climate change “is the biggest story out there. It’s something that people are experiencing here and now, not 50 years from now. We're focusing on that human impact. Right now, the climate issue pretty much where the civil rights movement was in 1957,” he says, expecting it to be a topic of presidential debates in 2016.

“Years of Living Dangerously” premieres on April 13, but Showtime is making it available to an audience beyond its subscriber base on multiple platforms. The first episode is accessible now on YouTube, on Showtime.net, Showtime on Demand, the Showtime Anytime mobile app and as an iTunes video podcast.